Traditional legacy and first generation IP PBX systems have significant challenges in terms of their scalability and redundancy characteristics. For example, such systems only provide for discrete hardware nodes at different locations and, if failure of a single node occurs, the entire system could stop working. Also, the limited feature set and networking capabilities of these systems restrict the amount of available expansion and user mobility. The enormous level of complexity of such legacy systems, combined with the cumbersome hardware requirements, makes them costly to own and maintain and undesirable for a modern IT environment.
Legacy PBX systems grew complex over many years, with different components melded together as new functionality was added, either as new components or layered on top of an existing component. Legacy PBX systems generally were not designed from the ground up. Also, little has changed in the unified communications industry over the last decade. The result of this ‘building on top of older systems’ was that administrators were left to cope with multiple element managers to manage individual components. Typically each element or component offered by a legacy vendor has its own architecture and history, was developed by a completely different team, or resulted from earlier technology acquisitions. They might run on different operating systems, require different middleware stacks, have independent database requirements, and drive different operating needs. They all come with their individual management interface—an element manager. As complexity grew the need for a manager of managers arose, offering yet another administration interface that only covers a small subset of the manageable functionality of the underlying components. Only highly trained experts can handle such systems, which drives cost up and prevents end users from becoming self-sufficient for moves, adds, and changes.